The demand for functional safety requirements continues to rise in high reliability applications, such as electronic applications for use in the automotive industry. These functional safety requirements specify that safety critical circuits should have the ability to detect and react to single point failures that may lead to malfunctions of the overall system. Among other components, a safety critical circuit may include a multi-input analog-to-digital converter (ADC) that processes analog input signals. Typically, a multi-input ADC includes a multiplexer and a core circuit. The multiplexer selects an analog input from multiple input channels, while the core circuit samples the selected input channel. Conventional diagnostic schemes primarily focus on fault detection of the core circuit but provide little to no coverage on the multiplexer side. To meet the increasing demand for function safety, there is a need for a diagnostic scheme that provides more comprehensive coverage on systems incorporating ADC devices.